Check valves in their broadest sense are well known for a variety of applications. One purpose of a check valve, such as when it is used in an area of a structure that experiences a liquid and gas interface, is to allow the egress of gas but to prevent the substantial flow of liquid. Such a purpose has been found useful, for example, in the area of water cooler design and fabrication.
In the field of bottled water coolers that are typically found in the home or office, a cooler housing supports an upwardly open reservoir that supplies users with water on demand via dispensing faucets or the like. The cooler housing and reservoir are designed to support a water bottle of three or five gallons (U.S.) capacity that is typically inverted to allow water to flow downwardly into the reservoir to a level sufficient to cover an open bottle mouth formed in the bottle neck. In normal operation, downward water flow from the bottle is accompanied by an upward exchange of air or gas from the reservoir into the bottle, and this gas-water exchange between the overlying bottle and the underlying reservoir continues until the water level of the reservoir rises sufficiently to cover the bottle mouth, at which point further air or gas exchange is halted and consequent downward water flow is stopped. As water is dispensed from the faucets that are supplied by the reservoir, the water level lowers to the point where the water level is below the bottle mouth, at which point the gas-water exchange may resume to enable additional water to flow downwardly into the reservoir. The general construction of water coolers is described in U.S. Pat. No. 6,167,921 B1 of Busick; U.S. Pat. No. 6,029,860 of Donselman; U.S. Pat. No. 6,003,318 of Busick; U.S. Pat. No. 6,123,232 of Donselman; U.S. Pat. No. 5,676,278 of Beyer; and U.S. Pat. No. 5,667,103 of Donselman, all of which are incorporated by reference herein.
The reservoir interior is typically designed to communicate with ambient air so that when the water level of the reservoir lowers due to typical water dispensing by users, ambient air takes its place prior to the gas-water exchange that replenishes the reservoir. Thus the upper reservoir chamber may be provided with an air filter so that air cannot enter the reservoir except by passing through the air filter medium. The description of such air filters in communication with water cooler reservoirs is found in U.S. Pat. No. 6,167,921 B1 to Busick and in U.S. Pat. No. 6,029,860 to Donselman, both of which are incorporated by reference herein. To protect such air filters from water flow and/or to prevent upward water flow therethrough in the event of reservoir overfilling, such as might occur with the use of a cracked bottle, an air filter unit may include a check valve in the air filter port, as can be found U.S. Pat. No. 6,167,921 B1 to Donselman, which appears to be a typical ball valve arrangement.
One problem that has now been encountered in the known check valves used in water cooler air filter units is that although these check valves may prevent the substantial flow of liquids beyond them, they are less than ideal in returning to their normally open position following the lowering of the liquid or water level of the reservoir. The known check valves that are manufacturable and cost effective suffer from valve sticking or valve structure distortion. This results in an internal pressure for any gas in the reservoir of substantially less than ambient, which has been found to substantially diminish the flow rate of dispensed fluids, such as water, from the dispensing faucets or outlets of the cooler. For example, it is believed that a known check valve comprising an imperforate disk and ring seal in a housing that includes an air filter media has experienced such a difficulty. Further, it is believed that the typical ball valve arrangement may suffer from similar disadvantages in performance, manufacturability and/or cost effectiveness.
Consequently there is a need for a cost effective and manufacturable check valve for a liquid—gas interface, that is normally open to permit gas passage but will close to substantially stop the flow of liquid in one direction and will reliably open to allow gas to flow in the other direction upon experiencing a low vacuum pressure differential across the valve structure from, for example, the reservoir of a water cooler, that may be of less than two inches (5.08 cm) of water column.
It would also be desirable if the check valve were readily manufacturable as a part of an air filter assembly, in which the check valve is so configured to protect the air filter from exposure to substantial quantities or flows of liquids, which unit is cost effectively constructed and simple to manufacture, so that the unit may have application in a typical water cooler or other such liquid dispensing structures that include a reservoir or the like.